Calibration Supplier Selection - Calibration & Temperature & Work Instructions

Jerry Eldred

Forum Moderator
Super Moderator
Having been on all sides of the fence regarding calibration suppliers (I have been both a user of calibration suppliers, and have worked in the third party industry), I am generally distrustful of third party suppliers. Let me qualify that. First, that is strictly my own opinion (because I am personally aware of what things third party suppliers do in the practice of their business). Secondly, I have had some of the same experiences on the other side of the fence.

I won't muddy the waters of this post with that laundry (I'll save it for another day). Bottom line - Verify, Verify, Verify.

So if we totally disregard making the auditor feel warm and fuzzy, we have the very important issue of our internal warm and fuzzy. Anyone who uses an external calibration supplier must have a good method to ascertain what services you need, and a method for assuring you get those services. There are many levels you can take that to. I have seen practices such as a Vendor Evaluation Form mailed to the supplier to have them complete and return, that being the extent of the verification. I am not at all comfortable with that approach.

It would get too complicated to try to respond in detail to this sort of issue. Suffice that there must be in place a good audit program on a periodic basis, a method for assuring the quality of the received calibration services.

Requiring certification to ISO, QS, A2LA, NVLAP or other recognized body is a great baseline. That will make it a lot easier to evaluate the lab considered. If they have no certification and no plans, personally, I would not even consider using them, because as stated in the earlier post, you have no baseline.

But certification by a considered lab to above standards is still only a baseline. That certificate doesn't guarantee much. In ISO (I am not an ISO guru), if your company writes a policy that you will do second rate calibrations, and you consistently follow that policy to perform those second rate calibrations, then you are in compliance (sorry, the politically correct term these days is "conformance"). But they are still second rate calibrations. The certification only says they have a functional quality system.

The importance of evaluation comes beyond that. If it is an OEM calibration lab, and the certificate is specifically for the calibration services, that certificate will have more value. But outside of that instance, further evaluation needs to be done.

A couple of key points include verification of documentation used to write procedures. Does their documentation require them to include ALL steps included in original manufacturers procedures? If so, when you evaluate, do they acutally include ALL steps in their intrenal documented calibration procedures used on your equipment. In the caliper example, I think the systemic issue is not whether they calibrated to your specified points, but whether they calibrated the calipers to a full procedure (things like checking surfaces with monochromatic light and optical flats, checking high, mid-scale, low scale and zero repeatability), or do they just perform one arbitrary check with whatever gauge block happens to be on the bench? Procedures must be adequate. That is a common problem I have seen in calibration suppliers. I can't emphasize heavily enough the importance of assuring that they use adequate methodology for procedure writing. If your calipers are calibrated by a lab that does not use adequate procedure methodology, first thing I would call into question is the last audit that was done by your company on that lab. If there was no previous audit, there needs to be one, and business should be pulled out of a dis-reputable lab.

As for special requirements, that is entirely a separate issue. If you have a specialized use for the calipers, you need to specify a specialized procedure for your calipers (and expect to pay extra for it).

TO pull back from my rambling, one of the original questions regarding if they only calibrated up to 4 inches, and you use at 4 to 6 inches. I will assume this is a 6 inch caliper (for discussion purposes). If they did not calibrate it to its full range, and unless they stated that it was a limited calibration, I would view it that they did not do what they said they would do. If you have any instrument with a given set of specs, and it is calibrated by a third party lab, they are implying that they verified it met those specs unless otherwise stated. If they did not do that, then they simply were not honest and did not calibrate the unit properly, irregardless of how good or bad their procedural methodology or quality system is. Hold them accountable. They didn't do what they promised.



Fully vaccinated are you?
Calibration Supplier Selection

From: manus
Newsgroups: misc.industry.quality
Subject: Re: Simple Questions - Calibration & Temp. Work Inst.

>> 1) Criteria for selection of calibration suppliers. At our last ISO
>> audit, the auditor said that we should have a procedure of how we select
>> critical service suppliers like calibration services. Any ideas?
>The easiest way around this is to choose a laboratory which is accredited to
>ISO Guide 25. This should give you and your auditor the confidence that the
>lab complies to more stringent criteria than ISO and eliminate the need for
>you auditing the lab.

The only problem with Guide 25 (now ISO 17025) is that is does NOT address the quality system. It only addresses what a laboratory must do for its business.

ISO 9001 and ISO 9002 require in section 4.6 that during the selection and evaluation of a supplier is that you must look at their quality system... Guide 25 or its equivalents do not address this topic because 9001 and 9002 are supposed to do that.

The question also is not to give the auditor a "warm fuzzy" feeling, but rather give you, the company, a valuable tool in gauging whether or not your supplier is actually doing something that is of good value for the money you pay to them.

For example, if you have a calibration laboratory give you a certificate for a high precision micrometer that just says it has been calibrated and was found to be in tolerance, gives a few blurbs about meeting a couple of specifications (one of which is magically Guide 25) a date, a new due date, a couple of serial numbers for traceability and so on but has not numerical data... this certificate is not satisfactory to even meet ISO 9001 or 9002.

You need the data from the laboratory to make a determination if the micrometer's measurement uncertainty is sufficient to your purpose. Let say this is a 6 inch caliper and the ID jaws are not in tolerance but the OD jaws are (most dis-reputable labs only do the OD jaws) and you rely heavily on the ID jaws for your product. What would you do? If you use the caliper at 4 inches to 6 inches and they only calibrated up to 4 inches and the caliper is not accurate in the area that you use... what would you do?

Also, the information that was in tolerance is actually not very informative. What is the tolerance that they used to make that determination? If they used the manufacturer's specifications, are they applicable to the actual micrometer, or did they just use a standard catalog (some show this information, but may be incorrect)?

The above actually happens more often than we care, even when the laboratory is supposedly certified to the standards that we ask for.

But let's lay that issue aside and take up the next.

You want the calibration laboratory to give you the data, and say actually what is happening with you measuring equipment on the certificate. Or, you find that they are not calibrating the 4" to 6" range on your caliper and want them to make a corrective action to their system.

Without a quality system in place, or a least some of the vital sections of a quality system, would they be able to know how to effectively make a change in their system?

Some would make the arguement that ISO 9000, QS 9000, or some other is not needed to implement quality in their company. I would agree up to the point that a quality system standard is not the end. But irregardless, you the company, for ISO 9001 and ISO 9002, are required to evaluate (look at) the supplier's quality system. It doesn't say how, it doesn't require you to force them to implement ISO, it just says you evaluate. If they meet your requirements and needs, then document that and go on using them. Slan Leat!

Phil McManus
Top Bottom